Marble (toy) - Wikipedia

A marble is a small spherical toy often made from glass, clay, steel, plastic or agate.These balls vary in size. Most commonly, they are about 1 cm (1 ⁄ 2 in) in diameter, but they may range from less than 1 mm (1 ⁄ 30 in) to over 8 cm (3 in), while some art glass marbles for display purposes are over 30 cm (12 in) wide.